For monitoring automated machine tools at important force connecting points on the machine, multicomponent force measuring sensors or strain sensors are used which divide the force flow into several coordinates. These signals are compared continuously with setpoints or predetermined values. Such machines, which operate through the so-called "witching hours", are CNC-controlled machine tools like turning and milling centers. They operate fully automatically and at the slightest deviation from the target state, a tool change or machine stop is initiated.
Such monitoring systems are already obtainable today from various machine makers as special equipment. Also available commercially are the necessary multicomponent force and strain sensors. The corresponding electronics and associated software are supplied by a number of specialized enterprises.
In recent years it has been shown that besides the machining forces, moments and strains, machine noises or structure-borne noise is another mechanical variable capable of constituting a further useful component for monitoring machining operations. Already there are boring machine monitoring devices which detect tool breakage through the alteration of the structure-borne noise spectrum. For grinding operations also, structure-borne noise measurement has proved of interest.
Measuring structure-borne noise from machining operations, as also from the drive parts, is of interest in the frequency range from 0.5 to 50 kHz. Usually, it is measured with high-frequency accelerometers. Transducers suitable for such analyses can be procured commercially today. Often, they are structure-borne noise transducers employed in automobile engineering for measuring detonation. Such transducers are big and less suited for fitting in machine tools.
The present invention combines measuring of force with structure-borne noise, and strain with structure-borne noise, to open up new application possibilities. The advantages are as follows:
Only one sensor installation point is needed. PA1 Only one cable connection is needed. PA1 In the domain of finish machining, structure-borne noise measuring may yield information additional to the force or strain measurement. In rough machining, the force or strain measurement, as the case may be, tells more than measuring the structure-borne noise.
In many applications, the two modes--force and strain measuring and structure-borne noise measuring--are complementary.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a force and structure-borne noise transducer according to the invention for one or more force components, with structure-borne noise sensor arranged centrally;
FIG. 2 shows the transducer of FIG. 1 with integrated bracing nut;
FIG. 3 shows the transducer of FIG. 1 with integrated key bracing element;
FIG. 4 is a cross-sectional view of a surface strain transducer with built in structure-borne noise sensor; and
FIG. 5 is a cross-sectional view of a bore strain transducer with built in structure-borne noise sensor.